/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * kernel/pthread/pthread_mutextrylock.c
 *
 *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <unistd.h>
#include <pthread.h>
#include <semaphore.h>
#include <sched.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include "pthread/pthread.h"

/****************************************************************************
 * Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: pthread_mutex_trylock
 *
 * Description:
 *   The function pthread_mutex_trylock() is identical to pthread_mutex_lock()
 *   except that if the mutex object referenced by mutex is currently locked
 *   (by any thread, including the current thread), the call returns immediately
 *   with the errno EBUSY.
 *
 *   If a signal is delivered to a thread waiting for a mutex, upon return from
 *   the signal handler the thread resumes waiting for the mutex as if it was
 *   not interrupted.
 *
 * Parameters:
 *   mutex - A reference to the mutex to be locked.
 *
 * Return Value:
 *   0 on success or an errno value on failure.  Note that the errno EINTR
 *   is never returned by pthread_mutex_trylock().
 *
 * Assumptions:
 *
 * POSIX Compatibility:
 *   - This implementation does not return EAGAIN when the mutex could not be
 *     acquired because the maximum number of recursive locks for mutex has
 *     been exceeded.
 *
 ****************************************************************************/

int pthread_mutex_trylock(FAR pthread_mutex_t *mutex)
{
	int status;
	int ret = EINVAL;

	svdbg("mutex=0x%p\n", mutex);
	DEBUGASSERT(mutex != NULL);

	if (mutex != NULL) {
		int mypid = (int)getpid();

		/* Make sure the semaphore is stable while we make the following
		 * checks.  This all needs to be one atomic action.
		 */

		sched_lock();

		/* Try to get the semaphore. */

		status = pthread_mutex_trytake(mutex);
		if (status == OK) {
			/* If we successfully obtained the semaphore, then indicate
			 * that we own it.
			 */
			mutex->pid = mypid;
#ifdef CONFIG_PTHREAD_MUTEX_TYPES
			if (mutex->type == PTHREAD_MUTEX_RECURSIVE) {
				mutex->nlocks = 1;
			}
#endif
			ret = OK;
		}

		/* pthread_mutex_trytake failed.  Did it fail because the semaphore
		 * was not avaialable?
		 */

		else if (status == EAGAIN) {
#ifdef CONFIG_PTHREAD_MUTEX_TYPES
			/* Check if recursive mutex was locked by the calling thread. */

			if (mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->pid == mypid) {

				/* Increment the number of locks held and return successfully. */

				if (mutex->nlocks < INT16_MAX) {
					mutex->nlocks++;
					ret = OK;
				} else {
					ret = EOVERFLOW;
				}
			} else
#endif

#ifndef CONFIG_PTHREAD_MUTEX_UNSAFE
				/* The calling thread does not hold the semaphore.  The correct
				 * behavior for the 'robust' mutex is to verify that the holder of
				 * the mutex is still valid.  This is protection from the case
				 * where the holder of the mutex has exitted without unlocking it.
				 */

#ifdef CONFIG_PTHREAD_MUTEX_BOTH
#ifdef CONFIG_PTHREAD_MUTEX_TYPES
				/* Check if this NORMAL mutex is robust */

				if (mutex->pid > 0 &&
					((mutex->flags & _PTHREAD_MFLAGS_ROBUST) != 0 ||
					mutex->type != PTHREAD_MUTEX_NORMAL) &&
					sched_gettcb(mutex->pid) == NULL)
#else /* CONFIG_PTHREAD_MUTEX_TYPES */
				/* Check if this NORMAL mutex is robust */

				if (mutex->pid > 0 &&
					(mutex->flags & _PTHREAD_MFLAGS_ROBUST) != 0 &&
					sched_gettcb(mutex->pid) == NULL)
#endif /* CONFIG_PTHREAD_MUTEX_TYPES */
#else /* CONFIG_PTHREAD_MUTEX_ROBUST */
				/* This mutex is always robust, whatever type it is. */
				if (mutex->pid > 0 && sched_gettcb(mutex->pid) == NULL) 
#endif
				{
					DEBUGASSERT(mutex->pid != 0);	/* < 0: available, >0 owned, ==0 error */
					DEBUGASSERT((mutex->flags & _PTHREAD_MFLAGS_INCONSISTENT) != 0);

					/* A thread holds the mutex, but there is no such thread.
					 * POSIX requires that the 'robust' mutex return EOWNERDEAD
					 * in this case. It is then the caller's responsibility to
					 * call pthread_mutx_consistent() fo fix the mutex.
					 */

					mutex->flags |= _PTHREAD_MFLAGS_INCONSISTENT;
					ret = EOWNERDEAD;
				}

				/* The mutex is locked by another, active thread */

				else 
#endif /* CONFIG_PTHREAD_MUTEX_UNSAFE */
				{
						ret = EBUSY;
				}

			}
			
			/* Some other, unhandled error occurred */
			else {
				ret = status;
			}

		sched_unlock();
	}

	svdbg("Returning %d\n", ret);
	return ret;
}
